Method for gasifying finely divided fuel with circulating gas



Oct. 18, 193 8. H, SCHMALFELQT 2,133,479

METHOD FOR GASIFYING FINELY DIVIDED FUEL WITH CIRGULATING GAS Filed Nov. '7, 1935 Mos-TE 6/9 1 2 OPEN W W v0 ZONE Patented Oct. 18, 1938 METHOD FOR GASIFYING FINELY DIVIDED FUEL WITH CIRCULATING GAS Hans Schmalieldt, Kassel, Germany Application November 7, 1935, Serial No. 48,729 In Germany November 26, 1934 3 Claims.

This invention relates to the process of producing gas from finely divided fuel and has reference particularly to the application of this procass to fine or dust coal.

5 My invention has for its object to introduce into the process of producing gas the step of providing a superpressure at any point in the path of travel of the fuel between the gasifler an each regenerator.

In the accompanying drawing, one form of apparatus, adapted to carryout the steps of the process is illustra'tively exemplified.

Referring to the drawing, a denotes a gasifier, and b the nozzles by means of which the finely divided fuel is introduced into the gasifier. The circulating gas heated. to 'a. high temperature by the regenerators di and d2 enters the gasifier alternately at m and c2, 'gasifles the coal dust in giving up heat, and escapes together with the freshly formed combustible gas at e. The regenerators di and. 112 are alternately heated by the furnaces f1 and in, the gasand air conduits m, 11 or 92 and Z2 respectively, of the corresponding furnaces to be opened'each time during the heating and closed each time during the cooling of the regenerators. The waste gas slide valves m1 and m: are likewise alternately open and closed during the heating and gasiiying. The circulating gas to be pre-heated, consisting of water vapour or of water vapour mixed with water gas,

or of a mixture of water vapour" and the gas produced, alternately enters the regenerators through the slide valves 91 and p: and comes into the gasifier through the connections 01 and C2.

The inlet passages for the hot circulating gases steam, e. g. together with water gas of diiferent" composition. or hydrogen and carbon dioxide or producer gas.) preferably in such a way that the cross section at this point is reduced for -80%. The nozzleshaped narrowing of the connecting conduits need not be arranged at the entrance into the gaslfier, but may be provided at any other point of the connecting conduit. However, the narrow-'-- ing of the conduit at the entrance into the gasi- The narrowing is proportioned fler presents the advantage that the high admission speed of the hot circulating gases flowing into the gasifiercauses a good circulation or a continuous interwhirling of the gas masses in the gasifler. Consequently the fine coal particles to 5 be gasifled are permanently maintained in suspension so that the gasification is accelerated.

If the nozzle, for example, is so dimensioned that the pressure in front of the nozzle during the flow of the circulating gas is about 2000 10 mms. water column and if the pressure difierence is maintained at 2 mms. water column between the gasifier and the regenerator on heat, the value of the gas flowing in an undesired direction orfthe heating side is only part of the circulating current, i. e. therefore only about a 30th part of the quantity of circu- "lating gas flows either as flue gas into the circulating gas or as circulating gas out of the gasifier into the flue gas of the generator on heat. The quantity of gas flowing in an undesired di rection has thus been reduced to an allowable minimum.

However, even when the pressure difi'erence between gasifler and the regenerator on heat is considerably greater, for example amounts to 20 mms. water column, the value of the gas flowing in an undesired direction is always only a tenth part of the circulating gas. I

The superpressure produced in the connecting path between the regenerating zone and the gasifying zone for sealing may be' used advantageously to circulate or to maintain in movement the gas masses in the gasifying zone by means of the speed increase of the flowing gases resulting from said superpressure during the passage of the gas stream from the gasifying regenerator; thereby the carbonaceous particles are kept in suspension. I

Consequently the construction of the gas inlet according to the invention, e. g. the nozzleshaped construction of the circulating gas inlet, results in such a reduction of the quantity of unaccounted for gas, that hot valves can be readily omitted, so that a regulated, economical working is possible. A slight dilution of the circulating gas can also be put up with, same as a slight loss of circulating gas.

It is, however, possible, according to the invention, to obtain an absolutely tight closure ii care is taken that the pressure in the regenerator wheat is always higher (0.1- mms. water column) than the pressure in the gasifler, which can always be attained by corresponding adjustment of the wastegas slide valves m. The measure necessary for this consists in introducing justed, that during the greatest permissible pressure difference this is just sufiicient to force the whole quantity of sealing steam into the gasifier. In the case of a small pressure difierence only a portion of the sealing steam flows into the gasifier, whereas the remainder passes ofi into the regenerator on heat. The steam, introduced into the gasifier, evidently does not cause a dilution of the circulating gas, but rather has a'useful efiect, as this steam is utilized to assist the gasification. The quantity of steam passing into the heating regenerator. likewise does not have a prejudicial effect as it is relatively small. In any case gas losses and dilution of the generated gas and also afterburning at any point not desired are avoided.

The difference in pressure between the regenerator on heat and the gasifier may be of the range of 0.3-4 mms. water column pressure but it may be also -100 mms. or, if necessary, slightly more. The pressure in the gasifier itself may vary between any limits; e. g. it may be regulated to 20350 mms. water column.

The carbonaceous fuel, finely divided, may be -e. g.: mineral coal, charcoal, lignite, peat or the like.

Naturally the pressure in the gasifying regenerator must be higher than in the gasifier.

Having thus described the invention, I claim: 1. In the herein described process for gasifying finely divided carbonaceous fuel by periodically circulating gases in series through a regenerating zone and a gasifying zone and in the alternate.

periods reheating the gases in the regenerating zone to 700-1600 C., the steps which comprise permanently choking the flow of the gas at a predetermined point of the path from the regenerating zone to the gasifying-zone, producing a substantial pressure difference between said two zones during the circulation period, and introducing sealing steam into said path during the heating period.

2. In the herein described process for gasifying finely divided carbonaceous fuel by periodically circulating gases in series through a regenerating zone and a gasifying zone and in the alternate periods reheating the gases in said regenerating zone to 700-1600 C., the steps which comprise permanently choking the gas flow of the gas at a predetermined point of the path from the regenerating zone to the gasifying zone, producing a pressure difference of about 290-5000 mms. water column between said two zones during the circulation period, and iniroducing sealing steam into said path during the heating period, the pressure in the regenerating zone being kept during the latter period from 0.1 to mms. water column higher than in the gasifying zone by regulating theamount of waste gas discharged from the regenerating zone during the heating period.

3. In the herein described process for gasifying finely divided carbonaceous fuel in two alternating periods, in which gases are circulated in series through a regenerating zone and a gasifying zone and heated to 700-1600 C. in a second regenerating zone during one of said periods, while the gases are heated to 700-1600 C. in said first-mentioned regenerating zone and circulated in series through said second regenerating zone and the gasifying zone during the alternate period, the steps which comprise permanently choking the flow of gas at two predetermined points in the paths from said regenerating zones, respectively, to said gasifying zone, producing a substantial pressure difference between the regenerating zone on circulation and the gasifying zone, and introducing sealing steam into the path between said regenerating zone 0 heat and the gasifying zone. v

HANS 

